Field of the Invention
The invention relates to a method for monitoring an optical system having a front lens disposed immediately at a combustion chamber. It also relates to a device suitable for accomplishing the method.
In the combustion of fossil fuel or refuse in a combustion chamber, fluctuations in the calorific value of the fuel or of the fuel mixture occur because of the different origin of the fuel and/or because of the heterogeneous composition of the refuse. These fluctuations increase pollutant emission of the combustion process. These disadvantages also exist in the combustion of industrial residual material. In the case of which, the combustion of solid and liquid as well as gaseous fuels is usually provided simultaneously. Given knowledge of the parameters characterizing the combustion process, the firing control can be optimized, and thus the combustion process as well.
A device for combustion analysis can determine the parameters characterizing the combustion process. The device uses an optical system having a front lens disposed immediately at the combustion chamber, for example, to detect intensity values of the light of the combustion process that, in their totality, yield an image of a flame of the combustion process. The spatially resolved intensity values of the image can then be used, for example, to determine the temperature distribution and the concentration distribution of reaction products arising in the process of combustion. Such a device and a method suitable for operating the device are disclosed in German Published, Non-Prosecuted Patent Application DE 197 10 206 A1.
German Published, No n-Prosecuted Patent Application DE 28 47 935 A1 discloses a device for carrying out a method for finding pollutants on specimens in transmitted light, and for signaling changes in the transillumination of the specimen. Cleaning a transparent body as a function of the degree of pollution is disclosed in German Published, Non-Prosecuted Patent Application DE 29 04 126 A1.
A particular quality of the intensity values used for the analysis is important for reliable optical monitoring of the combustion process, and for a control based thereon. However, because waste products arise during combustion, pollution of the front lens of the optical system used to determine the intensity values, and thus a worsening of the quality of the data can arise. Consequently, there is a need at regular time intervals for time-consuming maintenance and/or cleaning of the front lens of the optical system, which is in direct contact with the combustion chamber. These time intervals are usually determined using empirical values and do not depend on the actual requirement for maintenance and/or cleaning of the front lens of the optical system. For safety reasons, maintenance and/or cleaning work is therefore usually provided more frequently than required for operating reasons. However, this is attended by long down times and a low level of availability of the optical system, and thus also of the combustion chamber.